By winning five separate Grands Prix this week, Metro Rail's Dumb Ways To Die viral from Australia has unquestionably been the star of Cannes but what does its success say about the industry's faith in traditional television advertising?

The signals are mixed, to say the least. Dumb Ways To Die shared the award with a campaign for Toshiba/Intel which told a story across six online episodes (each of which was about seven minutes long). But according to Mark Sweney's piece announcing the winners the "jury was somewhat disdainful about a growing trend of agencies submitting very long pieces of video content used for online campaigns".

This disdain might have had more impact if they hadn't given this year's grand prix to a series of films with an aggregate length of about 40 minutes and a three-minute long viral.

There is no doubt that Dumb Ways To Die has caught Cannes's imagination in an unprecedented fashion. Admittedly, its record-breaking haul of Grands Prix is partly a reflection of its eligibility in an unusually broad range of categories at the ever-expanding event but there's clearly more to it than that.

Measured by YouTube viewings, Dumb Ways To Die has been a huge success. Some reports suggest it has been viewed 500m times (though YouTube's own measure suggests the figure is closer to 50m) – either way, that's more viewings than Australia has people, an impressive achievement for a film that aimed to draw attention to dangerous behaviour on railway platforms and at level crossings in the state of Victoria.

Many are championing Dumb Ways To Die for its effectiveness – but what's meant by that? Has it been labelled effective because it's been shared by millions of people on social networking sites or because it's meaningfully reduced rail deaths?

No one can deny that it's a fun piece of work and that it's been widely shared but if that's enough to win the biggest prize at Cannes, next year's winner could be a video of a kitten doing something cute with a logo slapped on the end.

This is the fourth time in five years that Cannes has handed its top prize to films longer than two minutes. Only Old Spice's 2010 winner The Man Your Man Could Smell Like can be regarded as a traditional TV commercial.

Agencies around the world submitting their TV campaigns at a cost of €700 a film have a right to feel disgruntled. Every piece of work made for television is constrained by the requirement to abide by stringent regulations and the need to create films that won't cost a fortune to run during an ad break.

Over the past 60 years, advertising creatives and film directors have quite brilliantly negotiated these constraints to make a fantastic array of television commercials and, until 2009, they could dare to dream that their best work might be rewarded with the ultimate accolade at the world's most important advertising festival.

It's no longer a level playing field. Television commercials are being beaten to the grand prix by films made with the complete freedom afforded by the internet. It's like turning up to a football match to find your opponents have 15 players on the field and then discovering that the spectators are so distracted by the number of goals the other team are scoring that they don't even notice the disparity.

It's time for Cannes to create a separate category for online work and thereby ensure that next year's Film Lion grand prix is handed to a genuine television commercial.